Tuesday, February 5, 2008

Rising CO2 Levels: A Double Whammy for the Food Supply*

Some critics of the case for global warming make light of concerns over rising levels of atmospheric carbon dioxide.

Increased carbon dioxide is good for plant growth, they say. Some don't concede that the planet is warming up at all, despite a preponderance of opinion to the contrary among mainstream scientists.

But they maintain that even "if" the world should warm, Canada comes out a winner.

First, the argument goes, warmer climate means a longer growing season. It pushes the temperate zone in which field crops flourish farther north. This means more land can be used for agriculture.

Second, all that carbon dioxide in the atmosphere will stimulate plant growth. Thus, we get more farmland and better growing conditions.

However, the latest bit of news should be equally alarming to those concerned about global warming and the "What, me worry?" faction.

Research published by three scientists at Southwestern University in Texas suggests that the price of rising carbon dioxide levels in the atmosphere is sharply falling nutritional value in staple crops upon which 40 per cent of the world's population relies for its dietary protein.

Daniel Taub, Brian Miller and Holly Allen analysed more than 220 experiments in which plants were exposed to levels of carbon dioxide that ranged from the present ambient level to about double the existing level. They discovered that as the carbon dioxide in the atmosphere goes up, the protein in wheat, barley, rice, potatoes and soy beans diminishes, in some cases quite sharply.

Barley lost 15.3 per cent of its protein, potatoes lost 14 per cent, rice and wheat lost almost 10 per cent. Soy beans fared better, but even they lost 1.4 per cent of protein.

As these plants absorb more carbon dioxide into their tissues, the researchers found, they do so at the expense of other compounds, including those which are essential parts of proteins.

This may all seem rather esoteric, but a 10- to 15-per-cent shortfall in the protein available to 40 per cent of the world's population should make everyone sit up and take notice because the effects would be felt pretty quickly by the other 60 per cent, too.

Cereal grains, particularly barley, are key components in feed for the animals - chickens, pigs, cattle - that provide much of the protein in the developed world. A 15-per-cent reduction in the nutritional value of animal feed could only mean less efficiency for farmers and rising costs for consumers of meat, eggs and dairy products as well as for consumers of the two cereal grains - wheat and rice - that dominate world supply.

Well, the solution's easy, some might counter. Just use the additional land that comes available as temperate zones move north to increase production and that will offset any falling nutritional values.

But the climate change jigsaw is complicated and what seems logical doesn't necessarily follow. For example, the quality of soils in northern latitudes is much poorer than the deep, rich soils that now comprise the North American and European breadbaskets.

In Canada, 95 per cent of the land mass will never be suitable for field crops. It doesn't matter what the climate is like, you can't grow wheat on glaciated rock or mountains. And agriculture requires stable climatic conditions; the evidence suggests global warming will bring the opposite.

Worldwide, a drop in nutritional value of cereals and potatoes is compounded by other difficulties.

Rising sea levels is one. The most productive arable land for most of humanity lies at the present sea level in coastal regions. That's because the most fertile land tends to be either old seabeds or in river estuaries and coastal plains like the Fraser delta, carried there by millions of years of erosion. Rising sea levels threaten this land with flooding and salt contamination.

The inability of impoverished nations to purchase fertilizer to boost production to meet nutritional shortfalls is another problem.

So, we may face a double whammy of constrained production and degrading food supply. Small wonder the researchers conclude that "The effect of atmospheric carbon dioxide on crop protein therefore seems likely to be of genuine importance for human nutrition in and beyond the 21st century."